1. Field of the Invention
The present invention relates to a printed circuit board unit including first electrically-conductive terminals fixed and exposed on a board in a matrix and second electrically-conductive terminals having flexibility arranged in a matrix, for example. The second electrically-conductive terminals are disengageably brought in contact with the corresponding first electrically-conductive terminals.
2. Description of the Prior Art
A land grid array (LGA) socket is well known as disclosed in “Land grid array sockets for server applications”, J. S. Corbin et al., IBM J. RES. & DEV., Vol. 46, No. 6, p. 763-778, November, 2002, for example. The LGA socket is utilized to mount a large scale integrated (LSI) package. The LGA socket has lower electrically-conductive terminals arranged on the lower surface of a socket board to be respectively received on electrically-conductive pads on a printed wiring board. Upper electrically-conductive terminals are arranged on the upper surface of the socket board. The upper electrically-conductive terminals are connected to the corresponding lower electrically-conductive terminals, respectively. The upper electrically-conductive terminals receive corresponding electrically-conductive terminals of the LSI package. The LGA socket serves to establish electric conduction between an electronic component package board and the printed wiring board in this manner.
The LSI package is urged against the printed wiring board. A plate is utilized for urging. The plate is overlaid on the LSI package. An urging force is applied to the four corners of the plate toward the printed wiring board. Distortion in the plate leads to reduction in the urging force on the center of the plate. This results in a failure in electric conduction between the upper electrically-conductive terminals and the corresponding electrically-conductive terminals of the LSI package and/or between the lower electrically-conductive terminals and the electrically-conductive pads on the printed wiring board, even if the urging force is enhanced as much as possible. In particular, enhancement in rigidity of the socket board leads to increase the possibility of failure in electric conduction.